Fermented soymilk with a monoculture of Lactococcus lactis

Comprehensive studies on the stability of yogurt-type fermented soy beverages during refrigerated storage using dairy starter cultures

Introduction

This study aimed to assess the feasibility of utilizing commercially available dairy starter cultures to produce yogurt-type fermented soy beverages and evaluate the fundamental properties of the resulting products.

Methods

Sixteen different starter cultures commonly used in the dairy industry for producing fermented milks, such as yogurt, were employed in the study. The study investigated the acidification curves, acidification kinetics, live cell population of starter microflora during refrigerated storage, pH changes, water-holding capacity, texture analysis, carbohydrates content, and fatty acid profile of the yogurt-type fermented soy beverage.

Results and Discussion

The results demonstrated that the starter cultures exhibited distinct pH changes during the fermentation process, and these changes were statistically significant among the cultures. The acidification kinetics of different cultures of lactic acid bacteria showed characteristic patterns, which can be used to select the most suitable cultures for specific product production. The study also revealed that the choice of starter culture significantly influenced the starter microorganisms population in the yogurt-type fermented soy beverage. Additionally, the pH values and water-holding capacity of the beverages were affected by both the starter cultures and the duration of refrigerated storage. Texture analysis indicated that storage time had a significant impact on hardness and adhesiveness, with stabilization of these parameters observed after 7-21 days of storage. Furthermore, the fermentation process resulted in changes in the carbohydrate content of the soy beverages, which varied depending on the starter culture used.

Flavour by design: food-grade lactic acid bacteria improve the volatile aroma spectrum of oat milk, sunflower seed milk, pea milk, and faba milk towards improved flavour and sensory perception

BACKGROUND

The global market of plant-based milk alternatives is continually growing. Flavour and taste have a key impact on consumers' selection of plant-based beverages. Unfortunately, natural plant milks have only limited acceptance. Their typically bean-like and grassy notes are perceived as "off-flavours" by consumers, while preferred fruity, buttery, and cheesy notes are missing. In this regard, fermentation of plant milk by lactic acid bacteria (LAB) appears to be an appealing option to improve aroma and taste.

RESULTS

In this work, we systematically studied LAB fermentation of plant milk. For this purpose, we evaluated 15 food-approved LAB strains to ferment 4 different plant milks: oat milk (representing cereal-based milk), sunflower seed milk (representing seed-based milk), and pea and faba milk (representing legume-based milk). Using GC‒MS analysis, flavour changes during anaerobic fermentations were studied in detail. These revealed species-related and plant milk-related differences and highlighted several well-performing strains delivered a range of beneficial flavour changes. A developed data model estimated the impact of individual flavour compounds using sensory scores and predicted the overall flavour note of fermented and nonfermented samples. Selected sensory perception tests validated the model and allowed us to bridge compositional changes in the flavour profile with consumer response.

CONCLUSION

Specific strain-milk combinations provided quite different flavour notes. This opens further developments towards plant-based products with improved flavour, including cheesy and buttery notes, as well as other innovative products in the future. S. thermophilus emerged as a well-performing strain that delivered preferred buttery notes in all tested plant milks. The GC‒MS-based data model was found to be helpful in predicting sensory perception, and its further refinement and application promise enhanced potential to upgrade fermentation approaches to flavour-by-design strategies.

Antifungal Preservation of Food by Lactic Acid Bacteria

Fungal growth and consequent mycotoxin release in food and feed threatens human health, which might even, in acute cases, lead to death. Control and prevention of foodborne poisoning is a major task of public health that will be faced in the 21st century. Nowadays, consumers increasingly demand healthier and more natural food with minimal use of chemical preservatives, whose negative effects on human health are well known. Biopreservation is among the safest and most reliable methods for inhibiting fungi in food. Lactic acid bacteria (LAB) are of great interest as biological additives in food owing to their Generally Recognized as Safe (GRAS) classification and probiotic properties. LAB produce bioactive compounds such as reuterin, cyclic peptides, fatty acids, etc., with antifungal properties. This review highlights the great potential of LAB as biopreservatives by summarizing various reported antifungal activities/metabolites of LAB against fungal growth into foods. In the end, it provides profound insight into the possibilities and different factors to be considered in the application of LAB in different foods as well as enhancing their efficiency in biodetoxification and biopreservative activities.

Characteristics of lipoxygenase-based and lipoxygenase-deficient soy yogurt with modified okara

Lipoxygenase-based and lipoxygenase-deficient okara were modified by Kluyveromyces marxianus fermentation, then adding modified okara back to the corresponding soymilk to prepare soy yogurt. The physicochemical properties, texture, and volatile components of soy yogurt were characterized. The results showed that okara modified by Kluyveromyces marxianus fermentation was rich in soluable dietary fiber and was imparted better water-holding capacity, swelling capacity, and oil-holding capacity. The soy yogurt with the modified okara was greatly enhanced in its appearance, texture and was relatively stable during storage. Moreover, lipoxygenase-based soy yogurt had a unique soybean flavor while lipoxygenase-deficient soy yogurt had a slight beany flavor and soybean flavor. This article guides a bio-modified method for okara and provides a theoretical basis for the further development and application of soy yogurt with high dietary fiber as well as lipoxygenase-deficient soy yogurt.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-021-01003-w.

Lactic Acid Bacteria-Fermentable Cereal- and Pseudocereal-Based Beverages

Plant beverages are becoming more popular, and fermented cereal- or pseudocereal-based beverages are increasingly used as alternatives for fermented products made from cow milk. This review aimed to describe the basic components of cereal- or pseudocereal-based beverages and determine the feasibility of fermenting them with lactic acid bacteria (LAB) to obtain products with live and active LAB cells and increased dietary value. The technology used for obtaining cereal- or pseudocereal-based milk substitutes primarily involves the extraction of selected plant material, and the obtained beverages differ in their chemical composition and nutritional value (content of proteins, lipids, and carbohydrates, glycemic index, etc.) due to the chemical diversity of the cereal and pseudocereal raw materials and the operations used for their production. Beverages made from cereals or pseudocereals are an excellent matrix for the growth of LAB, and the lactic acid fermentation not only produces desirable changes in the flavor of fermented beverages and the biological availability of nutrients but also contributes to the formation of functional compounds (e.g., B vitamins).

Effect of Lactic Acid Bacteria on the Lipid Profile of Bean-Based Plant Substitute of Fermented Milk

Biological processes of legumes may change their nutritional value of lipids, but there is no research on the fatty acid profile and their position distribution in fermented beverages obtained from germinated bean seeds. The present study aimed to determine the effect of fermentation by Lactobacillus strains on the fatty acid profile and their positional distribution in triacylglycerols of beverage obtained from germinated bean “Piękny Jaś Karłowy” (Phaseolus vulgaris) fermented by Lactobacillus strains. The population of lactobacilli (the pour plate method), pH, the fatty acid profile (gas chromatograph with a flame ionization detector), and the positional distribution of fatty acids in triacylglycerols (GC-FID) were determined before and after the fermentation of received beverages. The fermentation of beverages did not change the lactobacilli population (over 7 log₁₀ CFU/g), but changed pH (to 4.7–3.7 or 5.8–5.6), fatty acid profile, and the positional distribution of fatty acids were observed. The fermentation process contributed to an increase in the share of palmitic, stearic, and oleic acids in the fatty acid profile compared to that in raw bean seeds. The fermentation processes changed the share of individual acids in positions sn–1 and sn–3 depending on Lactobacillus strain used. Compared to non-fermented beverages, in most fermented beverages, a lower share of palmitic and stearic acids, as well as a higher share of oleic acid in the sn–2 were observed.

Volatile Molecule Profiles and Anti-Listeria monocytogenes Activity of Nisin Producers Lactococcus lactis Strains in Vegetable Drinks

This work aimed to evaluate the potential of 15 nisin producing Lactococcus lactis strains, isolated from dairy products, for the fermentation of soymilk and carrot juice. In particular, the acidification and the production of nisin in the food matrices were recorded. Moreover, three strains (LBG2, FBG1P, and 3LC39), that showed the most promising results were further scrutinized for their anti-Listeria monocytogenes activity and volatile molecules profile during fermentation of soymilk and carrot juice. Lactococcus lactis strains LBG2, FBG1P, and 3LC39 resulted the most interesting ones, showing rapid growth and acidification on both food matrices. The higher amounts of nisin were detected in soymilk samples fermented by the strain LBG2 after 24 and 48 h (26.4 mg/L). Furthermore, the rapid acidification combined with the production of nisin resulted in a strong anti-Listeria activity, reducing the pathogen loads below the detection limit, in carrot juice samples fermented by the strains LBG2 and FBG1P and in soymilk by the strain LBG2. The fermentation increased the presence of volatile molecules such as aldehydes and ketones with a positive impact on the organoleptic profile of both the fermented products. These results highlighted the interesting potential of three nisin producing L. lactis strains for the production of fermented carrot juice and soymilk. In fact, the fermentation by lactic acid bacteria, combined or not with other mild technologies, represents a good strategy for the microbiological stabilization of these products. Furthermore, the increase of molecules with a positive sensory impact, such as aldehydes and ketones, in the fermented products suggests a possible improvement of their organoleptic characteristics.

Effect of short chain inulin on the rheological and sensory characteristics of reduced fat set coconut milk yoghurt

The effect of short-chain inulin on the rheological and sensory properties of reduced fat set coconut milk yoghurt was studied with whole fat coconut milk yoghurt as reference. The concentration of short-chain inulin was varied at 0, 5, 10, 15, and 20% w/v respectively. All the yoghurt samples displayed higher elastic modulus G' than viscous modulus G". However, 15% inulin yoghurt had the highest value for G' & G". The 15 and 20% inulin yoghurts displayed high yield stress (1036.7 ± 2.39 & 368.23 ± 0.30 Pa). Addition threshold of 15% was established, beyond this level there was a significant decrease in the yield stress, firmness, cohesiveness and consistency values of the reduced fat yoghurts. Using Pearson correlation analysis, no correlation was observed between firmness and yield stress, Similarly, there was significant correlation between the yield stress and instrumental viscosity r = 0.957; p < 0.01. Furthermore, all yoghurt samples displayed strain thinning behavior except whole fat yoghurt. Carbohydrate was affected by inulin incorporation. Addition of short chain inulin improved sensorial characteristics such as taste, and flavor, but did not display significant difference in color and odor of yoghurt samples. This article is protected by copyright. All rights reserved.

Biofortification of riboflavin and folate in idli batter, based on fermented cereal and pulse, by Lactococcus lactis N8 and Saccharomyces boulardii SAA655

AIMS

Lactococcus lactis N8 and Saccharomyces boulardii SAA655 were investigated for their ability to synthesize B-vitamins (riboflavin and folate) and their functional role as microbial starters in idli fermentation.

METHODS AND RESULTS

In this study, ultra-high performance liquid chromatography and microbiological assay were used to determine the total riboflavin and folate content respectively. Increased levels of folate were evident in both L. lactis N8 and S. boulardii SAA655 cultivated medium. Enhanced riboflavin levels were found only in S. boulardii SAA655 grown medium, whereas decreased riboflavin level was found in L. lactis N8 cultivated medium. To evaluate the functional role of microbial starter strains, L. lactis N8 and S. boulardii SAA655 were incorporated individually and in combination into idli batter, composed of wet grounded rice and black gram. For the experiments, naturally fermented idli batter was considered as control. The results indicated that natural idli fermentation did not enhance the riboflavin level and depleted folate levels by half. In comparison with control, L. lactis N8 and S. boulardii SAA655 incorporated idli batter (individually and in combination) increased riboflavin and folate levels by 40-90%. Apart from compensating the folate loss caused by natural fermentation, S. boulardii SAA655 fermented idli batter individually and in combination with L. lactis N8 also showed the highest leavening character. Moreover, the microbial starter incorporation did not significantly influence the pH of idli batter.

CONCLUSION

Incorporation of L. lactis N8 and S. boulardii SAA655 can evidently enhance the functional and technological characteristics of idli batter.

SIGNIFICANCE AND IMPACT OF THE STUDY

UN General Assembly declared 2016 the International Year of pulses emphasizing the importance of legumes as staple food. Furthermore, this is the first experimental report of in situ biofortifcation of riboflavin and folate using microbes in pulse based fermented staple food. The current study suggests possible avenues for research towards an economical strategy to reduce B-vitamin deficiency among the consuming population.

Trends in dairy and non-dairy probiotic products - a review

Health awareness has grown to a greater extent among consumers and they are looking for healthy probiotic counterparts. Keeping in this view, the present review focuses recent developments in dairy and non-dairy probiotic products. All over the world, dairy probiotics are being commercialized in many different forms. However, the allergy and lactose intolerance are the major set-backs to dairy probiotics. Whereas, flavor and refreshing nature are the major advantages of non-dairy drinks, especially fruit juices. Phenotypic and genotypic similarities between dairy and non-dairy probiotics along with the matrix dependency of cell viability and cell functionality are reviewed. The heterogeneous food matrices of non-dairy food carriers are the major constraints for the survival of the probiotics, while the probiotic strains from non-dairy sources are satisfactory. Technological and functional properties, besides the viability of the probiotics used in fermented products of non-dairy origin are extremely important to get a competitive advantage in the world market. The functional attributes of dairy and non-dairy probiotic products are further enhanced by adding prebiotics such as galacto-oligosaccharide, fructo-oligosaccharide and inulin.

Studies on changes in microstructure and proteolysis in cow and soy milk curd during fermentation using lactic cultures for improving protein bioavailability

Cow milk curd was prepared using 2% v/v of Streptococcus thermophilus DG1 and a mixed culture (0.5:1.5 v/v) of S. thermophilus DG1 and Lactobacillus plantarum and incubating at 37 °C for 16 h. Soy milk curd was prepared using different ratios of lactic cultures as stated earlier and also a mixed culture containing S. thermophilus DG1, L. plantarum and Leuconostoc mesenteroides sub spp. mesenteroides in the ratio 1:1:1 v/v along with beet pulp (2% w/w) and incubating at 37 °C for 18 h. This improved functional and probiotic properties of curd. Structural changes in curd samples during fermentation were observed by Scanning Electron Microscope (SEM). Soy milk curd showed loosened structure. The degradation of proteins into peptides and amino acids were evaluated by SDS PAGE and amino acid analysis. Maximum production of amino acids i.e. cystine, histidine and asparagine were observed in both the cow and soymilk after fermentation.

Improvement of Experimentally Induced Hepatic and Renal Disorders in Rats using Lactic Acid Bacteria-fermented Soybean Extract (BiofermenticsTM)

The effects of lactic acid bacteria-fermented soybean extract (Biofermentics; BF) on experimental models of hepatic and renal disorders were investigated in vivo and in vitro. In rat, hepatitis induced by feeding of deoxycholic acid (DCA, 0.5 wt/wt, n = 6) or intraperitoneal injection of d-galactosamine (GMN, 500 mg/body wt, n = 6), the increase in serum AST (aspartate aminotransferase) and ALT (alanine aminotransferase) levels were inhibited significantly (P < 0.05) by feeding a diet containing 5% dried BF. Moreover, the BF-administered rat group showed lower concentrations of blood urea nitrogen and a larger amount of urine as compared with values in the control group. Pretreatment of primary cell cultures of rat hepatic and renal cells with BF prior to exposure to dichromate (K(2)Cr(2)O(7)) resulted in a marked decrease of dichromate-induced cytotoxicity as evaluated by the leakage of lactate dehydrogenase The levels of dichromate-induced lipid peroxidation, as monitored by malondialdehyde formation, were also reduced by pretreatment of hepatocytes with BF. These results suggest that BF may play a role in hepatic and renal disorders, and may be useful for maintaining health in humans as well.

The effect of prebiotics on production of antimicrobial compounds, resistance to growth at low pH and in the presence of bile, and adhesion of probiotic cells to intestinal mucus

AIMS

Screening of five bile salt-resistant and low pH-tolerant lactic acid bacteria for inhibitory activity against lactic acid bacteria and bacterial strains isolated from the faeces of children with HIV/AIDS. Determining the effect of prebiotics and soy milk-base on cell viability and adhesion of cells to intestinal mucus.

METHODS AND RESULTS

Lactobacillus plantarum 423, Lactobacillus casei LHS, Lactobacillus salivarius 241, Lactobacillus curvatus DF 38 and Pediococcus pentosaceus 34 produced the highest level of antimicrobial activity (12,800 AU ml(-1)) when grown in MRS broth supplemented with 2% (m/v) dextrose. Growth in the presence of Raftilose Synergy1, Raftilose L95 and Raftiline GR did not lead to increased levels of antimicrobial activity. Cells grown in the presence of Raftilose Synergy1 took longer to adhere to intestinal mucus, whilst cells grown in the absence of prebiotics showed a linear rate of binding.

CONCLUSIONS

A broad range of gram-positive and gram-negative bacteria were inhibited. Dextrose stimulated the production of antimicrobial compounds. Adhesion to intestinal mucus did not increase with the addition of prebiotics.

SIGNIFICANCE AND IMPACT OF THE STUDY

The strains may be incorporated in food supplements for HIV/AIDS patients suffering from gastro-intestinal disorders.